Support node 0.6.x

Hello,

Lot of people are still running on node 0.6.x. For example, Debian does not yet offer node 0.8 packages.

This change make sauce-connect-launcher work with node 0.6.x.

Note that [node-progress](https://github.com/visionmedia/node-progress) doen't support node 0.6 so you need to use the `no_progress` option.

Regards